Changed way test launch activities into split-screen windowing mode

Have test use methods launchActivitiesInSplitScreen and
launchActivityInSplitScreenWithRecents to launch activities into
split-screen which are more explicit in what should happen.

Test: self
Fixes: 70519287
Change-Id: If92ea4016415dc2a5d6f5dfd6e6c650b79c83278
10 files changed